"Is Bale worth that amount? This question will have to be asked in a year," said the Frenchman.

"Ten years ago, I recognised that I was not worth €75million. Nowadays I have a tendency to say the same, that no player is worth that.

"But two clubs agree a price without being forced to. That's football, unfortunately. It is difficult to understand. It is incomprehensible with all that is going on today."

Zidane, who will work alongside new coach Carlo Ancelotti, added: "Bale understands the impact of his arrival. He comes to the best club in the world, and does so with this huge transfer price.

"I have experienced this and for three months it was very complicated. I even considered whether it was best to leave. Then, if you focus on what happens on the field, things flow more naturally.

"My role will be to tell him to play as he knows and not to pressurise himself too much. He has incredible potential and is a player who has proven over the last three years to be the best out there.

"He also has room for improvement, he is only 24 and I think he can bring much to Madrid."

Barcelona president Sandro Rosell, who spent £50m on Neymar this summer, said: "I would not have spent Euros 100m for Bale, but they do it because their members allow them. I have nothing more to say."

But former Real Madrid star Ronaldo has claimed Bale and Cristiano Ronaldo can operated together.

The Brazilian said: "I think that these two players are going to work very well together in Madrid, they will triumph together with Madrid and the fans will enjoy them."